Fiber handling system with fuzz detection

ABSTRACT

An unwinding system includes a detector assembly configured to detect a position of a fiber unwound from a bobbin and the presence of fuzz. The system further includes a controller configured to adjust at least one of a lateral position or a rotational speed of the bobbin based on at least one of the position of the fiber tow or the presence of fuzz.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. Provisional Application Ser. No. 63/302,192 filed on Jan. 24, 2022, the contents of which are incorporated herein by reference.

BACKGROUND

During the manufacturing of ceramic matrix composites (CMCs), fibers are typically unwound from a bobbin to begin processing and wound onto rollers at some point in the process. The fibers may be made up of any number of individual filaments; in some cases 500, 1500, 2,000 or more individual filaments may be present in the fiber. During processing, individual filaments of the fiber may break at any place along the fiber path. Breakage is often indicated by the appearance of fuzz along the fiber, which frequently precedes breakage of the fiber itself. Thus, a need exists for a device that monitors the fiber during movement to accurately determine the location and condition of the fiber tow.

SUMMARY

Spooling and de-spooling tow coating systems utilize certain techniques to limit the amount of material losses. For example, active spool axial positioning systems may be used to control the unwind angle. Precise speed control for spools and de-spools may be achieved with a feedback loop to actively control tension. These techniques may be used to prevent breakage of individual filaments in a fiber tow which may result in material build up as fuzz causing tow losses at a minimum and entire process failures at worst.

During chemical vapor infiltration, material coated on the fiber tow may also be deposited on the internal reactor components. Optical detection of the buildup materials or fuzz is effective when a fiber tow is passed between detector and optical source. Use of optical elements can achieve wide parallel or nearly parallel optical beams from a small size optical source (point source). For example, a total internal reflection lens or a diffuser film or their combination may be used with LED light source to achieve a desired beam pattern.

According to one embodiment of the present disclosure, an unwinding system for unwinding a fiber from a bobbin is disclosed. The unwinding system includes a fiber suitable for forming a ceramic matrix composite wound on a bobbin defining a first axis, the fiber extending from the bobbin along a second axis transverse to the first axis. The system also includes a detector assembly disposed along the second axis and configured to detect the position of a fiber tow and the presence of fuzz. The system further includes a controller configured to adjust at least one of a lateral position or a rotational speed of the bobbin based on at least one of the position of the fiber tow or the presence of fuzz.

Implementations of the above embodiment may include one or more of the following features. According to one aspect of the above embodiment, the detector assembly may include an imaging sensor and a light source. The fiber tow is disposed between the light source and the imaging sensor. The imaging sensor may include at least one array of pixels disposed along a third axis that is perpendicular to the second axis and parallel to the first axis. The controller may be further configured to operate the detector assembly in a tow position detection phase and a fuzz detection phase. The controller may be also configured to switch between the tow position detection phase and the fuzz detection phase on a periodic basis. During the fuzz detection phase, the controller may be configured to count number of fuzz elements. The controller may be further configured to adjust at least one of a pixel value or exposure of the imaging sensor. The controller may also be configured to adjust intensity of the light source. The controller is configured to adjust at least one operational parameter of the imaging sensor or the light source.

According to another embodiment of the present disclosure, a method for unwinding a fiber from a bobbin is disclosed. The method includes unwinding a fiber suitable for forming a ceramic matrix composite from a bobbin defining a first axis, the fiber extending from the bobbin along a second axis transverse to the first axis. The method also includes passing a fiber tow through a detector assembly disposed along the second axis and configured to detect a position of a fiber tow and the presence of fuzz. The method further includes providing the position of the fiber tow and a presence of fuzz value to a controller. The method additionally includes adjusting at least one of a lateral position or a rotational speed of the bobbin based on at least one of the position of the fiber tow or the presence of fuzz value.

Implementations of the above embodiment may include one or more of the following features. According to one aspect of the above embodiment, the method may also include: illuminating the fiber tow by a light source of the detector assembly; and imaging the fiber tow at an imaging sensor of the detector assembly. The method may also include operating the detector assembly in a tow position detection phase and a fuzz detection phase. The method may further include switching between the tow position detection phase and the fuzz detection phase on a periodic basis. The method may additionally include counting a number of fuzz elements during the fuzz detection phase. The method may also include adjusting at least one operational parameter of the imaging sensor or the light source. Adjusting at least one operational parameter may also include adjusting at least one of a pixel value or an exposure of the imaging sensor. Adjusting at least one operational parameter may further include adjusting an intensity of the light source.

According to a further embodiment of the present disclosure, a method for unwinding a fiber from a bobbin is disclosed. The method includes unwinding a fiber suitable for forming a ceramic matrix composite from a bobbin defining a first axis, the fiber extending from the bobbin along a second axis transverse to the first axis. The method also includes passing a fiber tow through a detector assembly disposed along the second axis. The method further includes operating the detector assembly in a tow position detection phase to determine position of the fiber tow and adjusting at least one of a lateral position or a rotational speed of the bobbin based on the position of the fiber tow. The method additionally includes operating the detector assembly in a fuzz detection phase to determine a presence of fuzz value and adjusting at least one of the lateral position or the rotational speed of the bobbin based on the position of the presence of fuzz value. The method also includes switching operation of the detector assembly between the tow position detection phase and the fuzz detection phase.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be understood by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which:

FIG. 1 schematically shows an exemplary unwinding system for unwinding a fiber from a bobbin;

FIG. 2 schematically shows a portion of the exemplary unwinding system of FIG. 1 from another angle;

FIG. 3 shows an isometric view of an exemplary bobbin apparatus, such as for use with the exemplary unwinding system of FIG. 1 ;

FIG. 4 schematically shows an exemplary detector assembly, such as for use with the exemplary unwinding system of FIG. 1 ;

FIG. 5A schematically shows a portion of an exemplary unwinding system at different times during the unwinding process, showing the impact of the amount of fiber on the bobbin on the detection process;

FIG. 5B schematically shows a portion of an exemplary unwinding system at different times during the unwinding process, showing the impact of the amount of fiber on the bobbin on the detection process for a fiber longer than the fiber of FIG. 5A;

FIG. 6 is a flow chart showing an exemplary method of intelligently unwinding a fiber from a bobbin;

FIG. 7 shows background sensor images with no fiber present at three different light intensities;

FIG. 8 shows sensor images with a fiber present at three different light intensities, showing the resolution of the main tow and fuzz at different light intensities, as well as a camera image of the fiber and fuzz;

FIG. 9 shows a background sensor image with no fiber present, a sensor image with a fiber present, and the result of subtracting the background image from the image with a fiber present, in accordance with an embodiment of the present disclosure; and

FIG. 10 shows an LED intensity graph of the bottom image of FIG. 9 (sensor reading minus background) useful in detecting the presence of fuzz in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed fiber handling and detection systems are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

Reference is made in detail to specific embodiments, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation. It will be apparent to those skilled in the art that various modifications and variations may be made in the embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment may be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

While the following description is directed to the exemplary unwinding devices shown in the figures, it should be understood that the detector assembly and control algorithms described herein may be used in connection with any fiber handling system, especially systems designed for handling fibers suitable for forming a ceramic matrix composite, such as, for example silicon carbide (SiC) fibers. Other types of fiber handling systems with which the present detector assembly and control algorithms may be used or adapted for use include but are not limited to the systems disclosed in U.S. Pat. No. 10,118,792, U.S. Published Patent Application No. 2007/0099527, and International Application WO2015-041899A1, the entire disclosures of each of which are incorporated herein by this reference.

Directional terms such as top, bottom, and the like are used simply for convenience of description and are not intended to limit the disclosure attached hereto. Also, as used herein, the term “on” includes being in an open or activated position, whereas the term “off” includes being in a closed or inactivated position. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.

The present disclosure provides an intelligent fiber handling system along with methods of its use. In embodiments, the present fiber handling system uses at least one sensor (e.g., an optical sensor) during unwinding to assess the position of a fiber tow, and a system of motors and/or drivers that align the fiber tow unwinding from the bobbin into the downstream receivers (e.g., a pulley) so as to minimize processing damage of the individual filaments in the fiber as it leaves the surface of the wound fiber on the bobbin and enters the pulley. Each tow spool is driven by a motor and a drive. The motor may be a servo motor, a stepper motor, or a DC motor. Servo motor-type of drive system allows for extremely accurate velocity control within 0.001%. This precision helps maintain a consistent tension on the fiber tow. A closed loop tension feedback algorithm may be used as described in further detail below. A load cell measures the tension on the fiber tow. The speed of the servo motor may be increased or decreased to decrease or increase the tension, respectively. In particular, any scraping as the fiber unwinds from the bobbin, either with adjacent portions of the fiber on the bobbin and/or the bobbin surface, may be minimized by keeping the payoff angle (i.e., the first angle described below) near 90°. In embodiments, the sensor (e.g., a light sensor) is utilized to both establish the position of the fiber as it is payed off of the bobbin and to detect the presence of fuzz on or around the fiber tow, which may be a sign of process inefficiency or imminent breakage of the fiber tow (e.g., process failure). The bobbin can then be constantly aligned, in real-time, such that fiber tow is centered into the pulley. Additionally or alternatively, the tension on the fiber tow may be adjusted to reduce the presence of fuzz to improve process efficiency and avoid process failure. As such, the present intelligent system manages various aspects of the fiber handling, particularly when utilized within a vacuum chamber.

Improvements in tow speed/tension control may be achieved by using a servo motor with a high resolution at a low-speed setting. In embodiments, with a linear speed of 25 inches per minute and a circumference of about 12.5″, the target speed may be about 2 rpm +/−0.1 rpm. The target tension may be about 40 g with the +/−0.1 rpm modulation providing for tension increases of about +/−6 grams.

Referring to the drawings, FIG. 1 shows an exemplary unwinding system 10 for unwinding a fiber 12 a from a bobbin 14 rotatably mounted around an axle 16. Axle 16 defines a first axis 18 extending in an axial direction 20, as shown in FIG. 2 , such that bobbin 14 is rotatable around first axis 18. Additionally, bobbin 14 is controllably movable along axial direction 20 to control the angle of fiber 12 a coming off of bobbin 14 (the fiber is referred herein simply as a “fiber” while wound on the bobbin and referred to as a “fiber tow” once the fiber leaves the bobbin). Consequentially, the angle of fiber tow 12 going into pulley 22 is controlled. As shown, fiber tow 12 extends tangentially from a surface 15 of bobbin 14, and into pulley 22 positioned to receive fiber tow 12 from bobbin 14. Pulley 22 is rotatable around a second axis 24. In embodiments, pulley 22 is in a fixed location along second axis 24.

As more particularly shown in FIG. 2 , a detector assembly 150 is positioned between bobbin 14 and pulley 22. Detector assembly 150, which includes a light source 160 and a sensor assembly 170, is configured to determine the position of fiber tow 12 with respect to pulley 22 along at least one point of the length of fiber tow 12. In addition, detector assembly 150 is configured to detect the presence of fuzz on or near fiber tow 12. As stated, fiber tow 12 extends a length from bobbin 14 to pulley 22. When a tension is applied on fiber tow 12, the fiber length extends tangentially from surface 15 of bobbin 14 and tangentially into pulley 22. Thus, the length of fiber tow 12 between bobbin 14 and pulley 22 is substantially the same as the length L between first axis 18 and second axis 24.

Fiber tow 12 defines a first angle 19 with first axis 18 as it is unwound from surface 15 of bobbin 14. Similarly, fiber tow 12 defines a second angle 25 with second axis 24 as it is received into pulley 22. The unwinding system 10 is utilized to move bobbin 14 along axial direction 20 of first axis 18 (e.g., moving bobbin 14 along axial direction 20 of axle 16) such that the first angle and the second angle are kept as close to 90° as possible. For example, each of first angle 19 and second angle 25 may be maintained from about 80° to about 100°; in embodiments from about 85° to about 95°; in other embodiments from about 88° to about 92°. Thus, any fraying of fiber tow 12 is minimized as it enters pulley 22, since fiber tow 12 moves into pulley 22 such that fiber tow 12 avoids contact with pulley sides 23 and scraping against other fibers as it leaves the surface of wound bobbin 14.

Referring again to FIG. 1 , unwinding system 10 may be encased within a vacuum chamber 100. A pump 102 is fluidly connected to vacuum chamber 100 so as to adjust the pressure within vacuum chamber 100. As such, the environment 101 within vacuum chamber 100 may be controlled as desired. In particular embodiments, environment 101 within vacuum chamber 100 may be evacuated to an unwinding pressure of about 1 torr to about 5 torr (e.g., about 2 torr to about 3 torr) during the unwinding process. However, it should be noted that the presently described system may be used in any vacuum level, any pressure, or even in a chemical environment.

Controlling of first angle 19 and second angle 25 through lateral movement of bobbin 14 is particularly useful when the length L between first axis 18 and second axis 24 is relatively small with respect to the width W of bobbin 14 (e.g., within a vacuum chamber). Since the fiber 12 a is wound around bobbin 14 along most of its width W, the fiber 12 a is unwound from bobbin 14 from a changing point along its width. The closer bobbin 14 is to pulley 22, the more exaggerated first angle 19 and second angle 25 can become if bobbin 14 is not moved laterally in axial direction 20. For example, the length L of fiber tow 12 from bobbin 14 to pulley 22 may be about 50% to about 1,000% of the width of bobbin 14 along first axis 18.

Referring now to FIG. 3 , an exemplary bobbin apparatus 200 is generally shown that may be utilized with unwinding system 10. Bobbin apparatus 200 includes bobbin 14, controller 130, a motor 32 configured to rotate bobbin 14 around axis 18, and a motor 33 attached to bobbin 14 and configured to move bobbin 14 and motor 32 in axial direction 20. Motor 33 can actuate bobbin 14 laterally in axial direction 20 along the first axis 18 as controlled by controller 130 in response to real-time signals received at controller 130 from sensor 176 regarding the position of fiber tow 12 between bobbin 14 and pulley 22. Bobbin apparatus 200 may also include a magnetic drive mechanism for moving bobbin 14 along first axis 18.

Controller 130 may include a discrete processor and memory unit (not pictured). The controller 130 may include any suitable processor operably connected to a memory (not shown), which may include one or more of volatile, non-volatile, magnetic, optical, or electrical media, such as read-only memory (ROM), random access memory (RAM), electrically-erasable programmable ROM (EEPROM), non-volatile RAM (NVRAM), or flash memory. The processor may be configured to perform operations, calculations, and/or set of instructions described in the disclosure including, but not limited to, a hardware processor, a field programmable gate array (FPGA), a digital signal processor (DSP), a central processing unit (CPU), a microprocessor, etc. The processor may also include a microprocessor, or a combination of the aforementioned devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). Those skilled in the art will appreciate that the processor may be any logic processor (e.g., control circuit) adapted to execute algorithms, calculations, and/or set of instructions described herein.

It should be understood that a single controller may be used to execute the algorithms described herein to perform all calculations and control all operations of the present fiber handling system. Alternatively, two or more separate controllers may be employed to perform selected calculations and/or control selected functions while collectively performing all needed operations. Thus, for example as shown in FIG. 3 , a first controller 130 may be employed to control the rotational speed of motor 32, a second controller 130 a may be employed to control motor 33 and the axial position of the bobbin, a third controller 130 b may be positioned on the detector assembly 150 (see FIG. 4 ) to process data collected by sensor 176 and to control the scan rate of sensor 176 and the intensity of light emanating from light source 160. Those skilled in the art reading this disclosure will readily envision other combinations and configurations of controllers that may be used in carrying out the calculations and performance of functions of the algorithm described herein.

Additionally, the memory device(s) may generally include memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD), and/or other suitable memory elements. The memory can store information accessible by processor(s), including instructions that may be executed by processor(s). For example, the instructions may be software or any set of instructions that when executed by the processor(s), cause the processor(s) to perform operations. For the embodiment depicted, the instructions include a software package configured to operate controllers 130 (or controllers 130, 130 a, 130 b in certain embodiments) to, e.g., execute the exemplary method described below with reference to FIG. 6 .

As more particularly shown in FIGS. 1-3 , fiber tow 12 exits pulley 22 and is received into an idler pulley 34. Then, fiber tow 12 may be received from idler pulley 34 into a dancer pulley 36 that may be connected to a tension controller (e.g., a spring) 38. Tension controller 38 is generally configured to maintain a desired tension on fiber tow 12 as it is processed through unwinding system 10. In certain embodiments, tension controller 38 senses the load on dancer pulley 36 (i.e., tension on the fiber tow) and then responds to a change the tension on fiber tow 12 by acting on dancer pulley 36 and/or sends a signal to controller 130 to accelerate/decelerate rotation of bobbin 14.

In embodiments, the fiber 12 a may be a ceramic fiber such as silicon carbide suitable for forming a fiber reinforced ceramic matrix composite (CMC). Fiber 12 a may be made up of a plurality of filaments. The fiber may include any suitable number of filaments. In embodiments, the fiber includes 100, 500, 1,500, 2,000 or more filaments. The resulting CMC may be a continuous uniaxial or woven fibers of ceramic material embedded in a ceramic matrix. These materials are designed to have a relatively weak fiber-matrix bond strength compared to the matrix strength so as to increase overall composite strength and toughness. When the CMC is loaded above a stress that initiates cracks in the matrix, the fibers de-bond from the matrix allowing fiber/matrix sliding without fiber fracture. The fibers can then bridge a matrix crack and transfer load to the surrounding matrix by transferring tensile stresses to frictional interfacial shear forces. Such fiber reinforced CMCs have great potential for use in aircraft and gas turbine engines due to their excellent properties at high temperatures.

In embodiments, as seen in FIG. 4 , detector assembly 150 includes a frame 152 to which light source 160 and sensor assembly 170 are mounted. Light source 160 may include an LED, OLED, incandescence lamp, fluorescence lamp, or any other radiation source. In embodiments, the radiation source may be used in combination with optical elements configured to form parallel or nearly parallel beams relative to sensor 176. In embodiments, light source 160 includes an LED 162, a TIR (total internal reflection) lens 164, and a diffuser 166, providing an optical system that forms the beam profile and directs the light to sensor assembly 170. As those skilled in the art will appreciate, the intensity of light emanating from light source 160 may be adjusted by changing the current flowing through the LED. Different light intensities may be suitable for different purposes. For example, high intensity light may be particularly suitable for determining the position of the main tow, while lower intensity light may be more suitable for detecting the presence and amount of fuzz. In addition, electrical current (power) driving light source 160 may be adjusted during the operation to offset for the reduction of the source light intensity incident on sensor assembly 170 due to optical lens contamination and/or gradual degradation of the light source during operation.

Sensor assembly 170 includes a sensor 176, which may be any imaging sensor, such as charge couple device (CCD) or a complementary metal-oxide-semiconductor (CMOS) sensor capable of detecting light emanating from light source 160 with sufficient sensitivity to detect the presence and location of the fiber between bobbin 14 and pulley 22 and the presence of fuzz as fiber 12 passes between light source 160 and sensor assembly 170. In embodiments, sensor 176 may have any resolution and may have a 1×1024 pixel array providing an integer number indicating signal level for each pixel (e.g., 0 to 32767), where a low number corresponds to high light intensity falling on a pixel, and low light intensity gives a high number. Lens 175 is disposed on sensor 176 and is configured to focus the image (at given focal distance within a given focal depth 172) of the tow on sensor 176. As noted above, sensor assembly may include a controller 130 b to receive data from sensor 176, compare the received data to thresholds stored thereon, and generate control signals in response thereto. Inclusion of some of the control functions as part of the sensor assembly may be advantageous when detector assembly 150 (or at least sensor assembly 170) is positioned within vacuum chamber 100 to minimize the number of data transmission wires passing into and out of the vacuum chamber 100.

The configuration of light source 160 and sensor assembly 170 establish a focal depth 172 and field of view 174 for detector assembly 150 as shown in FIG. 4 . It should be understood that in embodiments, detector assembly 150 may be set up on a moving support to maintain the fiber tow within the focal depth of the sensor lens for improved detection for large length of fiber tow bobbins. Alternatively, a larger distance L between sensor assembly 170 and a light source 160 may be selected to use with an optical system (e.g., lens and diffuser 166), providing a detector assembly with larger depth of focus.

With reference to FIG. 5A, the fiber tow 12 includes a first fiber tow portion 112 a, representative of the fiber 12 a coming off the bobbin at a first time early in the process, and the fiber tow portion 112 a is within the focal depth 172 of detector assembly 150. At a time later in the process, a second fiber tow portion 112 b, representative of the fiber 12 a coming off bobbin 120 at a second, later time in the process, is still within the focal depth 172 of detector assembly. Thus, a shorter tow length (e.g., ˜500 m) does not produce a great deal of variation in tow position during unwind. In this example, movement of the detector assembly 150 of any component thereof is needed to ensure the fiber tow may be detected throughout the process.

As seen in FIG. 5B, however, where a longer length of fiber is provided on a larger diameter bobbin 120′, as fiber tow portion 112 ′a comes off the bobbin at a first time early in the process, fiber tow portion 112 ′a is within the focal depth of detector assembly 150. At a time later in the process, fiber tow portion 112 ′b is no longer within the focal depth of the detector assembly. Thus, a longer tow length (e.g., ˜2000 m), thicker filaments in the tow, or a thicker tow with a larger number of filaments will produce large variation of tow position and may interfere with detection of the fiber tow position or presence of fuzz by sensor assembly 170. In this example, movement of the detector assembly or of some component thereof may be needed to ensure the fiber tow can be detected throughout the process. Alternatively, a detector assembly 150 with a greater distance between light source 160 and sensor assembly 170 may be selected to provide a larger depth of focus without the need to move detector assembly 150 of any component thereof.

It should be understood that in embodiments, detector assembly 150 may be set up on a moving support to maintain the tow within the focal depth of the sensor lens for improved detection for large variations in the diameter of the fiber-filled bobbin from the beginning of the unwinding process towards the end of the unwinding process. Alternatively, a larger distance between a sensor and a light source may be selected to use with a sensor a lens with a larger depth of focus.

In embodiments, the optics may be modified to read in a wider path, or to chain multiple sensors together to read a ribbon of tow pre- and post-reactor to provide information on tow jumps, tow breaks, and other issues that would affect the process. Fewer fiber tows in the reactor will use less product, and mass flow controller (MFC) flow rates could be automatically adjusted based on the number of fiber tows passing through the reactor and/or automatically shutting down in the event that the tow breakage is detected.

Controller 130 may interrogate sensor assembly 170 at a pre-determined frequency, in embodiments about 60 Hz, and controls the timing and intensity of light emanating from light source 160 (e.g., to output a continuous or pulsed light of a high or low intensity). The fiber tow is passed in front of sensor assembly 170 and sensor 176 measures the position where the fiber tow is blocking the light. Detection of low light intensity that gives a number above a pre-determined threshold, indicates the position of the fiber tow. Detection of higher light intensity that gives a number below a pre-determined threshold, indicates that no material is present. Detection of intermediate light intensity that gives a number above a pre-determined threshold indicates that fuzz is present as described in more detail below in connection with FIGS. 8-10 . Sensor assembly 170 can generate signals indicative of the intensity of light sensed and transmit those signals to controller 130. Controller 130 is configured to move bobbin 14 laterally in axial direction 20 along axle 16 and/or to alert an operator of the presence and/or amount of fuzz detected.

FIG. 6 is a flow chart showing an exemplary computer-implemented method for fiber position and condition detection in accordance with aspects of the present disclosure. While the method of FIG. 6 illustrates a plurality of steps in a particular order, the steps need not all be performed in the same order as shown and may be performed in any suitable sequence.

During steps 500-512, controller 130 operates in a tow position detection phase, and at steps 500-506 configures detector assembly 150 to determine fiber tow position. At step 500, controller 130 sets average target pixel value for sensor 176. Controller 130 also receives a tow light intensity value, namely, the intensity of light source 160, at step 502, which may include light pulse rate. Light source 160 may be synchronized with the operation of sensor 176, to avoid continuous operation. Thus, light source 160 may be operated to only illuminate when sensor 176 is imaging, e.g., electronic shutter is open. This limits the amount of light produced by light source 160 thereby minimizing the amount of heat buildup.

The tow light intensity value may be stored in memory of controller 130 and/or provided from another controller, an input device (not shown), or another device controlling light source 160 (e.g., controller 130 b on sensor assembly 170, when present, which can determine the exposure value either by a preset value or by an algorithm hardcoded thereon). At step 504, controller 130 also receives the tow exposure value for sensor 176, which may be from 1 to 15,000 microseconds. When the fiber tow blocks the light, it causes high signal level number readings in the sensor array corresponding to the location of the fiber tow. The optics provide a focused image in the center pixels, and there is some distortion at the edges. To compensate for light variation and any distortion on the edges, controller 130 modifies the exposure time that it is measuring the light. The longer the exposure time, the lower the signal level numbers as the lower intensity light eventually saturates sensor 176.

When measuring fiber tow position, it may be beneficial to use a longer exposure time, so the higher signal level numbers appear where the main fiber tow exists while the less dense fuzz drops out of the picture. This position is used in a feedback loop to control the bobbin traverse motor in order to keep the fuzz peeling off the spool at a large angle to avoid scraping on the neighboring fiber tow and damaging the tow quality. The frequency of measurements may be lower than fuzz frequency measurements, e.g., below 60 Hz.

At step 506, controller 130 determines or sets a tow threshold signal value representative of the fiber tow being imaged by sensor 176. At step 508, controller 130 determines the position of the fiber tow relative to sensor 176. With reference to FIGS. 8 and 9 , the position of the fiber tow is shown as a dark line. The position may be presented as a position value based on the size of the array of sensor 176. Controller 130 then outputs a first output (position signal) at step 510 indicative of the fiber tow position. In particular, position of the fiber tow is adjusted by moving bobbin 14 as described above based on a corrective axial movement signal sent from controller 130 in step 512. The position adjustment may be done at any suitable frequency that is based on the sampling frequency of controller 130 and/or detector assembly 150. For a majority of the cycles (e.g., 9 out of 10), which may be from about 30 Hz to about 140 Hz, and in embodiments may be about 60 Hz, controller 130 continues to determine the fiber tow position.

Every 10^(th) cycle of the sampling frequency, controller 130 switches to a fuzz detection phase and performs steps 514-522, 514-526, or 514-530. By alternating the readings, the fuzz numbers may be corrected for where the center of the fiber tow is located, and the position numbers can compensate for heavier fuzz which might offset the measured position.

At steps 514-520, controller 130 configures detector assembly 150 to determine the presence of fuzz. At step 514, controller 130 sets an optimal target average pixel value for sensor 176. “Target average pixel value” is the average value of all pixels in the array. A low average, close to zero, would indicate a long exposure or high intensity light. A higher average would indicate a short exposure or low intensity light. Lower target averages will saturate most pixels with light and will only have pixels above zero when the fiber tow is blocking light from those pixels. Higher target averages will allow the pixels to pick up a smaller blockage of light, typically caused by fragments of the fiber tow indicating the presence of fuzz. Controller 130 also receives a fuzz light intensity value, namely, the intensity of light source 160 for imaging fuzz, at step 516. The fuzz light intensity may be lower than the fiber tow light position intensity value. The intensity value may be stored in memory of controller 130. At step 518, controller 130 also receives the fuzz exposure value for sensor 176, which may be from 1 to 15,000 microseconds, but is longer than the tow exposure value. When measuring fuzz level, it is beneficial to use a shorter exposure time so as to not saturate the sensor to the point of losing the fuzz. The exposure time may be just long enough to maintain a consistent background that may be negated to show at what level the fuzz is present.

At step 520, controller 130 determines or sets a threshold signal value representative of the fuzz being imaged by sensor 176. At step 522, controller 130 counts a number of consecutive peaks that are above a threshold. With reference to FIG. 10 , an exemplary plot of signal values from sensor 176 take during fuzz determination phase, with peaks 1, 2, 3, 5, 6, and 7 representative of fuzz and peak 4 representative of the fiber tow. If controller 130 determines that there are no peaks, due to lack of any material being detected by the sensor 176, then at step 524, controller 130 indicates that there is a broken fiber tow and outputs a second output at step 526, which may be an alarm or a stoppage command to system 10.

If only one peak is detected, which is indicative of only the fiber tow being present, then controller 130 switches back to tow position detection phase of steps 500-512 as described above.

If, however, controller 130 determines that there is a plurality of peaks (i.e., more than 2), this indicates that there are at least two objects present, one of which is the fiber tow. At step 528, controller 130 indicates that fuzz is present and at step 530 outputs a third output, which may be a command to system 10 to take corrective action by adjusting the speed and/or position of bobbin to reduce fuzz formation.

By providing a system capable of servo control and 0.01 rpm resolution, it is possible to get much tighter tension control on the fiber tow.

By measuring the amount of fuzz and intensity of the fuzz, controller 130 may also log information on what portions of the fiber tow are shedding fuzz and for how long, which may then be used as an indication of fiber tow quality. The amount of fuzz detected and on what parts of the fiber tow could be correlated to end product quality and/or need of maintenance.

FIG. 7 shows background sensor images (i.e., with no fiber present) generated by 75 consecutive sensor readings at 15,000 exposure and at three different light intensities. As can be seen in FIG. 6 , at the intensity provided by powering the LED at 30 mA, the sensor detects high light intensity falling on a pixel, and the system generates a low number for about the center third of the sensor's view. At the intensity provided by powering the LED at 50 mA, the sensor detects high light intensity falling on a pixel, and the system generates a low number for about the center two-thirds of the sensor's view. At the intensity provided by powering the LED at 100 mA, the sensor detects high light intensity falling on a pixel, and the system generates a low number for essentially the entire view of the sensor.

FIG. 8 shows sensor images with a fiber tow present generated by 75 consecutive sensor readings at 15,000 exposure and at three different light intensities to show the resolution of the main fiber tow and fuzz at different light intensities. A camera image of the fiber tow and fuzz are also shown in FIG. 7 for comparison. As can be seen in FIG. 7 , at the intensity provided by powering the LED at 30 mA, the sensor detects fuzz with better resolution compared to images at the intensity provided by powering the LED at 100 mA. On the other hand, at the intensity provided by powering the LED at 100 mA, the sensor detects the main fiber tow with better resolution compared to images at the intensity provided by powering the LED at 30 mA.

In embodiments, the controller includes software that will subtract the data from a background sensor image (i.e., with no fiber present—see the top image in FIG. 9 ) from a sensor image with a fiber tow present (see the middle image in FIG. 9 ). The result of subtracting the background image from the image with a fiber tow present is shown in the bottom image in FIG. 9 . In certain circumstances, this subtraction technique may provide sufficiently detailed information for the controller to adequately control movement of the bobbin and/or alert an operator of the condition of the fibers being processed on the fiber handling device.

FIG. 10 shows an LED intensity graph corresponding to the bottom image of FIG. 9 (sensor reading minus background) useful in detecting the presence of fuzz in accordance with an embodiment of the present disclosure. As can be seen in FIG. 10 , the most intense peak on the graph corresponds to the location of the main fiber tow. The graph also identifies a threshold value, above which any peaks are identified as fuzz. Where the graph is below the threshold, no fuzz is present.

Through the exemplary unwinding system 10 described herein, the fibers, usually in the form of long fiber tows, may be unwound from a bobbin (i.e., the fiber source) to begin further processing, such as coating and/or saturating with a slurry of matrix powder in suitable solvents and binders, are then may be wound onto a mandrel to form cylinders or sheets of matrix containing aligned fibers. The impregnated shapes made therefrom are at this stage of the process commonly termed “prepregs.” A prepreg may be reshaped as desired and ultimately formed into a preform for a composite article. The preform is subjected to a burn-out step to remove organic or other fugitive coating components. The preform is finally consolidated into a dense composite material by reaction with molten silicon at high temperature.

The fibers may be coated for several purposes such as to protect them during composite processing, to modify fiber-matrix interface strength and to promote or prevent mechanical and/or chemical bonding of the fiber and matrix. A number of different techniques have been developed for applying fiber coatings, such as slurry-dipping, sol-gel, sputtering and chemical vapor deposition (CVD). In a typical CVD process, fibers and reactants are heated to some elevated temperature where coating precursors decompose and deposit as a coating. CVD coatings may be applied either in a batch or continuous mode. In a batch mode, a length of fiber is introduced into a reactor and kept stationary throughout the coating process while reactants are passed through the reactor. In a continuous process, fibers and coating precursors are continuously passed through a reactor. The exemplary unwinding system 10 described herein is particularly suitable for providing a continuous fiber into such a process.

It should be understood that while the exemplary embodiments shown in the figures illustrate a single fiber tow being processed within the vacuum chamber, it is also contemplated that multiple bobbins may be provided within the vacuum chamber to process multiple fiber tows simultaneously.

Moreover, the disclosed structure can include any suitable mechanical, electrical, and/or chemical components for operating the disclosed fiber handling system or components thereof. For instance, such electrical components can include, for example, any suitable electrical and/or electromechanical, and/or electrochemical circuitry, which may include or be coupled to one or more printed circuit boards. As used herein, the term “controller” includes “processor,” “digital processing device” and like terms, and are used to indicate a microprocessor or central processing unit (CPU). The CPU is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions, and by way of non-limiting examples, include server computers. In some aspects, the controller includes an operating system configured to perform executable instructions. Those of skill in the art will recognize that suitable server operating systems include, by way of non-limiting examples, FreeBSD, OpenBSD, NetBSD®, Linux, Apple® Mac OS X Server®, Oracle® Solaris®, Windows Server®, and Novell® NetWare®. In some aspects, the operating system is provided by cloud computing.

In one aspect of the present disclosure, the disclosed algorithms may be trained using supervised learning. Supervised learning is the machine learning (ML) task of learning a function that maps an input to an output based on example input-output pairs. The ML model infers a function from labeled training data consisting of a set of training examples. In supervised learning, each example is a pair including an input object (typically a vector) and a desired output value (also called the supervisory signal). A supervised learning algorithm analyzes the training data and produces an inferred function, which may be used for mapping new examples. In various embodiments, the algorithm may correctly determine the class labels for unseen instances. This requires the learning algorithm to generalize from the training data to unseen situations in a “reasonable” way.

In various embodiments, the present system may include a neural network that may be trained using training data, which may include, for example, different fiber characteristics (e.g., fiber composition, fiber diameter, bobbin size, coating process, etc.). The algorithm may analyze this training data and produce an inferred function that may allow the algorithm to identify fiber disintegration or failure, based on the generalizations the algorithm has developed from the training data. In various embodiments, training may include at least one of supervised training, unsupervised training, and/or reinforcement learning.

In some aspects, a user can initiate a training session while watching operation to simplify setup on each unique fiber and processing conditions. When the fiber is deemed to be fuzz free, the user can open a training window which will then be used to calibrate or train the analytics for future anomaly detection. For instance, Linux®, which may run a Python® script, for example, may be utilized to effectuate prediction. In aspects, analytics may also be performed in the sensor using platforms such as Tensor Flow® lite.

In various embodiments, the neural network may include, for example, a three-layer temporal convolutional network with residual connections, where each layer may include three parallel convolutions, where the number of kernels and dilations increase from bottom to top, and where the number of convolutional filters increases from bottom to top. It is contemplated that a higher or lower number of layers may be used. It is contemplated that a higher or lower number of kernels and dilations may also be used.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with a fiber handling device.

In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer).

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements. 

What is claimed is:
 1. An unwinding system for unwinding a fiber from a bobbin, the unwinding system comprising: a detector assembly configured to detect both a position of a fiber tow including a multifilament ceramic fiber suitable for forming a ceramic matrix composite and a presence of fuzz on or adjacent to the fiber tow; and a controller configured to adjust at least one of a lateral position or a rotational speed of the bobbin based on at least one of the position of the fiber tow or the presence of fuzz.
 2. The unwinding system according to claim 1, wherein the detector assembly includes an imaging sensor and a light source.
 3. The unwinding system according to claim 2, wherein the fiber tow is disposed between the light source and the imaging sensor.
 4. The unwinding system according to claim 2, wherein the controller is configured to operate the detector assembly in a tow position detection phase and a fuzz detection phase.
 5. The unwinding system according to claim 4, wherein the controller is configured to switch between the tow position detection phase and the fuzz detection phase on a periodic basis.
 6. The unwinding system according to claim 4, wherein during the fuzz detection phase, the controller is configured to count a number of fuzz elements.
 7. The unwinding system according to claim 4, wherein the controller is configured to adjust at least one operational parameter of the imaging sensor or the light source.
 8. The unwinding system according to claim 4, wherein the controller is further configured to adjust at least one of a pixel value or an exposure of the imaging sensor.
 9. The unwinding system according to claim 4, wherein the controller is further configured to adjust an intensity of the light source.
 10. The unwinding system according to claim 4, wherein the controller includes: a first controller positioned on the detector assembly, the first controller configured to at least one of: operate the detector assembly in a tow position detection phase and a fuzz detection phase, switch between the tow position detection phase and the fuzz detection phase on a periodic basis, adjust at least one of a pixel value or an exposure of the imaging sensor, or adjust an intensity of the light source; and a second controller associated with a motor and configured to control the motor to adjust at least one of the lateral position of the bobbin or the rotational speed of the bobbin.
 11. A method for unwinding a fiber from a bobbin, the method comprising: unwinding a fiber from a bobbin defining a first axis, the fiber extending from the bobbin along a second axis different from the first axis; passing the fiber through a detector assembly disposed along the second axis and configured to detect a position of the fiber tow and a presence of fuzz; providing a value relating to the position of the fiber tow and the presence of fuzz to a controller; and adjusting at least one of a lateral position or a rotational speed of the bobbin based on at least one of the position of the fiber tow or the presence of fuzz value.
 12. The method according to claim 11, further comprising: illuminating the fiber by a light source of the detector assembly; and imaging the fiber at an imaging sensor of the detector assembly.
 13. The method according to claim 12, further comprising operating the detector assembly in a tow position detection phase and a fuzz detection phase.
 14. The method according to claim 13, further comprising switching the detector assembly between the tow position detection phase and the fuzz detection phase on a periodic basis.
 15. The method according to claim 14, further comprising: counting a number of fuzz elements during the fuzz detection phase.
 16. The method according to claim 15, further comprising: adjusting at least one operational parameter of the imaging sensor or the light source.
 17. The method according to claim 16, wherein adjusting at least one operational parameter includes adjusting at least one of a pixel value or an exposure of the imaging sensor.
 18. The method according to claim 16, wherein adjusting at least one operational parameter includes adjusting an intensity of the light source.
 19. A method for unwinding a fiber from a bobbin, the method comprising: unwinding a fiber from a bobbin defining a first axis, the fiber extending from the bobbin along a second axis different from the first axis; passing the fiber through a detector assembly disposed along the second axis; operating the detector assembly in a tow position detection phase to determine position of the fiber; adjusting at least one of a lateral position or a rotational speed of the bobbin based on the position of the fiber; operating the detector assembly in a fuzz detection phase to determine a presence of fuzz value; adjusting at least one of the lateral position or the rotational speed of the bobbin based on the presence of fuzz value; and switching operation of the detector assembly between the tow position detection phase and the fuzz detection phase.
 20. An apparatus for treating a fiber to be formed into a ceramic matrix composite, the apparatus comprising: a vacuum chamber having positioned therein: a bobbin; and a detector assembly having a radiation source and a sensor assembly and configured to receive a fiber unwound from the bobbin between the radiation source and the sensor assembly, the detector assembly configured to detect both a position of the fiber and a presence of fuzz on or adjacent to the fiber; one or more motors configured to adjust a lateral position of the bobbin within the vacuum chamber or a rotational speed of the bobbin; and a controller configured to adjust at least one of the lateral position of the bobbin or a rotational speed of the bobbin based on at least one of the detected position of the fiber or the detected presence of fuzz. 